When you are able to flex the frames, add gentle pressure using your fingers to remove one lens at a time. Point a hairdryer around the lenses to warm the plastic. Use this method if the hot water did not work. Just as with using hot water, the goal is to make the frames flexible. Again, do not use force with the lens. If the lens doesn't pop out the first time, apply more heat to the frames and keep trying.
You can pop your new lenses into the old frame while it is still flexible from the heat. You may need to apply a bit more heat from the hairdryer or soak again in hot water. Apply heat until the lenses pop in easily.